Transparent ceramic composite armor

ABSTRACT

Transparent ceramic armor consisting of a light weight composite formed bytilizing a face plate of transparent aluminum oxide or transparent magnesium oxide with a back-up plate of transparent plastic and the two plates bonded together with a transparent adhesive. This composite on test affords complete ballistic protection against 0.30 AP M2 projectiles at 0° obliquity with a muzzle velocity of 2770 ft. per sec.

SPECIFICATION

This invention relates to transparent ceramic armor designed to providelight weight ballistic protection primarily for aircraft against armorpiercing projectiles.

Presently available transparent armors are inefficient in providingballistic protection due to their inability to induce severe projectileshatter and their tendency to crack on impact.

It is the object of this invention to obtain adequate protection byshattering small arms projectiles with a light weight composite armorhaving a hard transparent ceramic face plate bonded by a transparentadhesive to a tough resilient transparent plastic back-up plate.

It is also the object of this invention to utilize this shattering ofthe projectile by the face plate which spreads the impact force per unitarea to reduce the requirements of the back-up plate, in that the excessenergy per unit area to be absorbed by the back-up plate isproportionately lessened.

This particular transparent armor has been designed and tested to affordcomplete protection against caliber 0.30 AP M2 projectiles with a muzzlevelocity of 2770 f.p.s., but obviously could be engineered for other andlarger projectiles.

A composite material that will meet these requirements was constructedwith commercially available materials using as the material for the faceplate, transparent magnesium oxide or aluminum oxide with a back-upplate of a transparent plastic a polycarbonate resin such as "Lexan" andthe two plates were bonded together with a transparent adhesive. Othertypes of transparent plastic backing materials such as glass,plexiglass, fiberglass, lucite etc., can be used in either a monophasicor multiphasic form.

The drawing illustrates the composition and dimensions of thetransparent armor plates actually tested, together with the protectionafforded by recording the ballistic limit of each, in which:

FIG. 1 is a composite of transparent armor 10, in which the face plate11 is transparent magnesium oxide, 0.50" thick, bonded with atransparent adhesive (not shown) to a back-up plate 12 of transparentplastic "Lexan", 0.75" thick, has an area density of 14 pounds persquare foot and provides a ballistic limit of 3220 f.p.s. forprotection;

FIG. 2 is a composite of transparent armor 13 in which the transparentface plate 14 is aluminum oxide, 0.250" thick, bonded with a transparentadhesive to a back-up plate of transparent "Lexan" 1.00" thick, has anarea density of 11.4 pounds per square foot and provides a ballisticlimit of 2435 f.p.s. which is not satisfactory for protection against aprojectile with a muzzle velocity of 2770 f.p.s. This deficiency may becorrected by increasing slightly the thickness of the face plate, suchas 0.10";

FIG. 3 is a composite of transparent armor 16 in which the transparentface plate is made up of two transparent plates 17 and 18 of aluminumoxide each 0.250" thick with a transparent back-up plate 19 of "Lexan"1.00" thick, all plates being bonded together with a transparentadhesive (not shown) and having an area density of 16.4 pounds persquare foot which has a ballistic limit of 3820 f.p.s. for protection.

The composite armor of this invention is designed to meet therequirements of ballistic protection with light weight ceramic materialthat is completely transparent and has an improved capability ofprotection as compared to standard steel armor of equal areal density.

This comparison is shown in the following table in which competentballistic protection is provided against caliber 0.30 AP M2 projectileswith a muzzle velocity of 2770 feet per second:

Areal Density

30 pounds per square foot for Laminated Glass

20 pounds per square foot for High Hardness Steel

10 pounds per square foot for Opaque Ceramic Composites

14-16.4 pounds per square foot for Translucent Ceramic and PlasticBack-up

14-16.4 pounds per square foot for Transparent Ceramic and PlasticBack-up

Areal density is a term used particularly in armor evaluation. Alsowhere the same materials are translucent and are employed in thecomposite armor, it should be noted that due to the elastic constant andthe accoustical velocity determinations that the results sought arepractically identical with that of the transparent plates.

What is claimed is:
 1. Transparent ceramic armor comprising a lightweight composite of transparent material adapted to shatter on impactprojectiles with a muzzle velocity of approximately 3000 f.p.s.,consisting of a transparent ceramic face plate backed by a transparentplastic plate and bonded thereto with a transparent adhesive soconstructed and arranged that the light weight composite affordscomplete ballistic protection against projectiles with a muzzle velocityof 3000 f.p.s. or less.
 2. Transparent ceramic armor comprising, a lightweight composite of transparent material adapted to shatter small armsprojectiles on impact, consisting of a transparent facing of magnesiumoxide adapted to spread the impact force of a projectile and bonded witha transparent adhesive to a transparent plastic backing adapted toabsorb any excess energy from impact on face plate, said backing reducedboth in ballistic requirement and in weight by the greater distributionof the impact force by the face plate whereby the composite providesimproved protection with transparent armor over standard steel armor ofequal areal density.
 3. Transparent ceramic armor comprising, a lightweight composite of transparent material adapted on impact to shatterprojectiles with a muzzle velocity of approximately 3000 f.p.s.,consisting of a transparent face plate of magnesium oxide adapted onimpact to spread and reduce the impact force per unit area and bondedwith a transparent adhesive to a transparent plastic backup plate as asafety factor to absorb excess energy of the impact together withfragments of the face plate and the projectile so constructed andarranged that the requirements of the back-up plate are materiallyreduced by the reaction of the face plate in reducing the impact forceper unit area to permit the light weight composite provide completeballistic protection against projectiles with a muzzle velocity of 3000f.p.s. or less.
 4. Transparent ceramic armor comprising, a light weightcomposite of transparent material with an areal density of 14.0 poundsper square foot adapted to shatter on impact projectiles with a muzzlevelocity of approximately 3000 f.p.s., consisting of a transparent faceplate of magnesium oxide 0.50" thick adapted on impact to spread andreduce the impact force per unit area and bonded with a transparentadhesive to a transparent plastic back-up plate 0.75" thick adapted toabsorb less excess energy per unit area due to the greater distributionof impact force per unit area by the face plate whereby the light weightcomposite provides improved protection with transparent armor overstandard steel armor of equal areal density.
 5. Transparent ceramicarmor comprising, a light weight composite of transparent material withan areal density 16.4 pounds per square foot adapted to shatter onimpact projectiles with a muzzle valocity of approximately 3000 f.p.s.,consisting of a transparent laminated face plate of two plates ofaluminum oxide each 0.250" thick adapted on impact to spread and reducethe impact force per unit area and bonded with a transparent adhesive toa transparent plastic back-up plate 1.00" thick adapted to absorb lessexcess energy per unit area due to the greater distribution of theimpact force per unit area by the face plate so constructed and arrangedthat the light weight composite provides improved ballistic protectionwith transparent armor over standard steel armor of equal areal density.6. A transparent ceramic armor comprising a light weight composite oftransparent material adapted to shatter on impact projectiles with amuzzle velocity of approximately 3000 f.p.s., consisting of atransparent face plate of aluminum oxide 0.5" thick adapted on impact tospread and reduce the impact force per unit area and bonded with atransparent adhesive to a transparent plastic back-up plate 1.00" thickreduced in ballistic requirement by the greater distribution of theimpact force on the face plate so constructed and arranged that thelight weight transparent composite has an areal density not exceeding16.5 pounds per square foot and provides complete ballistic protectionagainst projectiles with a muzzle velocity of 3000 f.p.s. or less.